Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations each radiating to define a respective coverage area in which wireless communication devices (WCDs) (also known as user equipment devices (UEs), whether or not operated by an end-user), such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. (In practice, a given cell site may include an antenna structure and associated equipment that is arranged as multiple such base stations, each radiating to define a respective coverage area.) In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
To provide robust wireless coverage across a given geographic area, a wireless service provider typically operates, in the geographic area, numerous base stations that each provide wireless coverage that overlaps with wireless coverage provided by one or more other base stations. These base stations may include a combination of macro base stations (typically designed to cover a wide geographic area and provide service generally) and small-cell base stations, such as femtocells (typically designed to cover a limited geographic area and provide service to a particular subscriber or group of subscribers). This combination of base stations may then provide wireless coverage over a broad area via a plurality of fully or partially overlapping coverage areas.
Base stations having overlapping wireless coverage with one another may be referred to as neighbors. For instance, in an example wireless network, a first base station may have as a neighbor a second base station having overlapping wireless coverage with the first base station. Then, as its neighbors, the second base station may have the first base station and one or more third base stations. The one or more third base stations may each provide respective wireless coverage that overlaps with the wireless coverage of the second base station. The degree of wireless coverage overlap between the neighboring base stations may vary over time as changing environmental conditions, network configurations, and other factors alter signal propagation. WCDs operating in the geographic area may hand over between overlapping wireless coverage (as provided by neighboring base stations) to maintain air interface communication with the network as they move from location to location.
For the purpose of identification, a cellular wireless network may assign a coverage area identifier to each coverage area within the cellular wireless network. Base stations and WCDs may indicate particular coverage areas by reference to their respective assigned coverage area identifiers. For instance, a base station may emit a pilot signal indicating a particular coverage area identifier that has been assigned to the base station. A WCD may detect the broadcasted pilot signal and then request to operate in the coverage of the base station by referencing, in a handover request, the particular coverage area identifier. The base station receiving the handover request may then facilitate hand over of the WCD via one or more communications with the base station indicated in the handover request.
Since there are a limited number of unique identifiers, coverage area identifiers are typically re-used within the cellular wireless network. Such re-use of coverage area identifiers may, however, cause an issue known as identifier conflict. In particular, identifier conflict may occur when two base stations having the same coverage area identifier are near enough to one another geographically that the coverage area identifier is ambiguous (in that a reference to the coverage area identifier could refer to either of the two base stations).
In an effort to prevent identifier conflict, the cellular wireless network typically assigns different coverage area identifiers to nearby base stations. For instance, in the example cellular network noted above, the first base station may receive a coverage area identifier that is different from any of its neighbors (e.g., the second base station). Since the first and second base station provide overlapping wireless coverage, assigning the same coverage area to these base stations may cause frequent ambiguity. Further, the first base station may receive a coverage area identifier that is different from any neighbor of the second base station (e.g., the one or more third base stations). Then, in operation, the second base station may distinguish between the first base station and the one or more third base stations using their different identifiers.
However, in some circumstances, unique coverage area identifiers may be unavailable to all base stations in a given geographic area. For example, deployment of a large number of closely-located base stations (such as may serve a densely-populated area) may exhaust the unique coverage area identifiers available for assignment and necessitate re-use of one or more coverage area identifiers among nearby base stations. As another example, deployment of multiple femtocells (or other small-cells) within the wireless coverage area of a macro base station may necessitate re-using coverage area identifiers among the multiple femtocells. In the example cellular network noted above, such deployments may necessitate assigning the same coverage area to the first base station as is presently assigned to a nearby base station (e.g., the second base station or one of the third base stations). Such identifier re-use may result in identifier conflict.